It could be a scene from a B-rated horror flick or a ridiculous kids' comedy: a bug-eyed moth deftly pilots a robotic vehicle, zig-zagging back and forth to seek out its target, a sweet-smelling lady moth. But this isn’t fiction; this bizarre scene actually happened in the laboratory of three Japanese researchers from the University of Tokyo. Their research is published in this week's issue of Bioinspiration and Biomimetics.

The goal wasn’t entertainment, although it was a likely byproduct. Instead, the researchers are interested in biologically-inspired robots that can recognize and seek out odors, such as a gas leak or a chemical spill.

For this type of sensory processing, nature is an excellent place to turn for inspiration, since tracking down odors is a key aspect of survival for many species. Plants and animals have evolved in response to all sorts of ecological problems, and adaptations found in the natural world have been very helpful in advancing technology of all kinds (see here and here for previous Ars coverage of biologically-inspired technology).

The researchers decided to use the silkmoth (Bombyx mori) as a model animal, since this insect's well-researched sensory system is highly attuned to chemical signals. Male silkmoths locate mates by tracking a strong pheromone, called bombykol, that is released by females. The males have a distinctive way of tracking these odors: they start out with an initial “surge” toward the smell, then zig-zag back and forth until they can localize it. While it appears erratic, zigging and zagging actually allows the moth to use their two antennae to hone in on the pheromone’s location by turning toward the antenna that is receiving the greater chemical signal.

Knowing this, the researchers decided use the silkmoth as a living “brain” to pilot a robot toward an odor.

Enter the robot. This two-wheeled vehicle had a polystyrene ball that functioned like the trackball on a computer mouse; the moth stood on top of the ball, and as it walked in any one direction, the ball would roll, directing the vehicle. The robot was also equipped with a single motor on each side, as well as sensors and microcontrollers that could calculate the trajectory and turn radius. The moth was placed (actually, it was glued) at the helm, ready to drive the little vehicle.

The experiment took place in a wind tunnel—set for less than 1 meter per second, to help distribute the odor—with a few drops of synthetic bombykol at one end and the moth-piloted robot downwind of the scent. A trial was considered a “success” if the robot could locate and reach the faux booty call at the other end of the tunnel within 210 seconds, without hitting either wall of the chamber.

The moths were surprisingly good (though somewhat erratic) drivers; all 19 moths were successful in reaching the bombykol within the time allowed.

My favorite video

To find out how the moths—and the rest of the robotic exoskeleton—would respond to unexpected challenges, the researchers threw them a few curveballs. First, they covered the moths’ visual fields, and the success rate dropped to a still-respectable 84.2 percent. They introduced a turn bias, which increased the forward rotation of the motor on one side, and the backward rotation of the motor on the other side, causing the vehicle to respond unevenly to the moth’s direction. The moths were still pretty good at the task, succeeding in 80.8 percent of the trials.

Finally, the researchers introduced a time delay of between 200 and 600 ms, creating a lapse between the moth’s movement and the vehicle’s response. The moths had no problem with the time delay on its own, but struggled when they experienced a time delay and a turn bias simultaneously.

Eventually, the moth’s role as driver will be replaced by technology; the end goal is a fully-autonomous robot with a “brain” that mimics the moth’s own sensory perception. The trials showed that the silkmoth’s sensory system is amazingly quick, responsive, and adaptive in an artificial situation, so now the challenge is to construct an actual prototype with these attributes. By determining how variables such as turn bias affect success, the researchers can predict the effects of—and account for—these variables as they continue to develop the robot. Gathering information about sensitivity and processing time can also help researchers decide the types and numbers of sensors to include.

Perhaps one day, the humble silkmoth will play a role in securing our safety from chemical spills and leaks. But until then, at least we have the video.

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Kate Shaw Yoshida
Kate is a science writer for Ars Technica. She recently earned a dual Ph.D. in Zoology and Ecology, Evolutionary Biology and Behavior from Michigan State University, studying the social behavior of wild spotted hyenas. Emailkate.shaw@arstechnica.com//Twitter@KateYoshida

This is both neat and scary at the same time. There is no doubt that we're going to continue to discover useful combinations between animals technology/robots. For quite some time the sensory and brain power of animals is going to be significantly better, and more adaptable in many ways than computer processing. Some of these combinations may be a lot scarier than this.

The goal wasn’t entertainment, although it was a likely byproduct. Instead, the researchers are interested in biologically-inspired robots that can recognize and seek out odors, such as a gas leak or a chemical spill.

Does the article indicate what else they got out of this than entertainment (and publicity)? It is hard to see what you could learn from this that they didn't already know. While you could get biologically-inspired by how a moth searches out a mate, the car doesn't seem to contribute to finding out. And a car driven by a living being is not a robot.

The goal wasn’t entertainment, although it was a likely byproduct. Instead, the researchers are interested in biologically-inspired robots that can recognize and seek out odors, such as a gas leak or a chemical spill.

Does the article indicate what else they got out of this than entertainment (and publicity)? It is hard to see what you could learn from this that they didn't already know. While you could get biologically-inspired by how a moth searches out a mate, the car doesn't seem to contribute to finding out. And a car driven by a living being is not a robot.

That utilizing a design based on two antenna and a moth brain is at least a good starting point?

"It could be a scene from a B-rated horror flick or a ridiculous kids' comedy: a bug-eyed moth deftly pilots a robotic vehicle, zig-zagging back and forth to seek out its target, a sweet-smelling lady moth."

"Perhaps one day, the humble silkmoth will play a role in securing our safety from chemical spills and leaks."

Uhhh yeah maybe if the moth is horney and the lady moth is covered in the chemical.

home in onHe used the clues to home in on the source of the flames.: We are homing in on a solution. Usage notes: The phrase originates in military use ...964 B (139 words) - 07:42, 9 December 2012

Per Webster'sDefinition of HONE IN

: to move toward or focus attention on an objective <looking back for the ball honing in — George Plimpton> <a missile honing in on its target — Bob Greene> <hones in on the plights and victories of the common man — Lisa Russell>

I'lll concede that there's contention about the usage, but 'hone in' is not incorrect as was originally suggested.

Reminds me of the time when Mythbusters tried to remotely control a shark by strapping electromagnets to its head. The contraption was heavy and so the shark just sank to the bottom and stopped moving.

The goal wasn’t entertainment, although it was a likely byproduct. Instead, the researchers are interested in biologically-inspired robots that can recognize and seek out odors, such as a gas leak or a chemical spill.

Does the article indicate what else they got out of this than entertainment (and publicity)? It is hard to see what you could learn from this that they didn't already know. While you could get biologically-inspired by how a moth searches out a mate, the car doesn't seem to contribute to finding out. And a car driven by a living being is not a robot.

If your goal is to come up with a search algorithm as good as the moth's, but your search vehicle's mobility is totally different than moth flight, that might make it difficult to compare the performance of your model to the performance of the moth. Constrain the moth's movements to the same mobility limitations as your model and those comparisons are easy.

It does seem funny to me though, just because the moth search strategy is pretty well understood. Aside from establishing a baseline for comparison, mostly what you are learning about here is how well they adapt to controlling the vehicle.

I say this having worked on experiments with other types of animals finding odor sources, robot implementation of search strategies, and computer modeling of search strategies. Computer modeling is pretty limited here because the structure of odor distribution is extremely complex and hard to simulate, especially at fast time scales (like moth flight speeds). Robots with real odor plumes are better testbeds.

There are arguments in favor of both, particularly that both are equally correct and useful in carrying different connotations. The etymology supports both developing in relatively similar timeframes, indicating that "hone in" may not have developed as originally an error of "home in." In either case, it's now considered relatively acceptable to use "hone in."

They glued the moth to the robot?!! That's despicable!!Anyway, I think the moth would have gotten there a lot more quickly and easily if they hadn't attached it to a robot. Leave it to a bunch of robotics geeks to just make things harder than they have to be.

I am interested in the transition from flight to walking. In the wild, the moths must primarily peform this navigation in flight. So, it has to be designed to deal with navigating in three diemensions. Once glued in, the moth switches to a walking strategy. Does it try to fly and once that does not produce any change switch to walking? Is the same strtegy used by the moth for 3D flying and 2D walking?

Ooh they just glue a stick to its back and tie it up there. Ah. I was like how it is walking when its glued on...but the picture provided the details.

This is only cool if the sensors they are trying to make are organic-computer sensors that replicate existing brain/organ function. Smell is the last sensory input that's behind on the move to digital.